The mechanics of breathing

Question 1

in terms of resistance to breathing what factors affect it? (2)

Answer 1

lung compliance

airway resistance

Question 2

what’s lung compliance?

Answer 2

the ease with which the lungs can be expanded

Question 3

what 3 factors affect lung compliance?

Answer 3

elasticity of lung tissue
mobility of chest wall
surface tension (of the alveoli)

Question 4

what does elastic recoil oppose?

Answer 4

inspiration

Question 5

what does elastic recoil aid?

Answer 5

expiration

Question 6

when looking at a graph showing lung pressure during the respiratory cycle, what would it look like if there was no airway resistance?

Answer 6

no curve on the graph

Question 7

how is compliance calculated?

Answer 7

change in volume (L)/ change in pressure cm H2O

Question 8

what unit is compliance given in?

Answer 8

litres/cmH2O

Question 9

what is the mobility of the thoracic cage?

Answer 9

the movement of the thoracic cage

Question 10

what causes surface tension?

Answer 10

intermolecular forces between molecules in a liquid

Question 11

what’s LaPlace’s law?

Answer 11

law describing the relationship between pressure (p), tension (T) and the radius of the alveolus (r)

Question 12

according to LaPlace’s law, how is pressure (p) calculated?

Answer 12

p= 2T/r

Question 13

how does pulmonary surfactant affect surface tension?

Answer 13

reduces it

Question 14

what does a reduced surface tension mean for complicance?

Answer 14

it increases it

Question 15

what does surfactant do to alveoli?

Answer 15

keeps uniform alveoli size

Question 16

what is neonatal respiratory distress syndrome?

Answer 16

lack of surfactant secretion in premature babies, reducing compliance
causes alveoli collapse on exhalation and makes it difficult to inflate lungs

Question 17

how many will die from neonatal respiratory distress syndrome without rapid treatment?

Answer 17

50%

Question 18

does neonatal respiratory distress syndrome have a good or bad income with treatment?

Answer 18

good

Question 19

what’s airway resistance?

Answer 19

major ‘non elastic’ source of resistance to gas flow

Question 20

how does increasing resistance affected gas flow?

Answer 20

it reduces it

Question 21

what is resistance mainly determined by?

Answer 21

radius

Question 22

how is resistance affected along the journey of airflow (trachea–> terminal bronchiole)?

Answer 22

it reduces (even though it’s getting smaller, we have more of the tubes)

Question 23

what 2 factors affect airway resistance?

Answer 23

lung volume

bronchial smooth muscle

Question 24

what do the bronchi do as the lung expands?

Answer 24

dilate

Question 25

as we grow up what happens to lung volume, therefore what happens to resistance?

Answer 25

it increases, therefore resistance reduces

Question 26

how does the parasympathetic nerve affect bronchi?

Answer 26

causes bronchoconstriction

Question 27

how does the sympathetic nerve and adrenaline affect bronchi?

Answer 27

causes bronchodilation

Question 28

what is forced vital capacity (FVC)?

Answer 28

amount of air that can be expired when there's been a forced inspiration

Question 29

how is airway resistance measured?

Answer 29

looking at forced vital capacity

Question 30

what can listening to breath sounds find?(2)

Answer 30

- presence of mucous/fluid | - absence of breath sounds- due to a collapsed lung

Question 31

what can pulmonary function be measured with?(2)

Answer 31

peak flow metre | spirometer

Question 32

what does a peak flow metre measure?

Answer 32

the speed at which you are able to breathe air out

Question 33

who are peak flow metres used by?

Answer 33

chronic asthmatics (on a regular basis) - to determine cause of asthma

Question 34

what does a spirometer measure?

Answer 34

lung pressure and volumes

Question 35

what type of breathing does a spirometer measure?

Answer 35

normal/ tidal breathing

Question 36

what is tidal volume?

Answer 36

the volume of air removed per breath

Question 37

what's the average tidal volume for men and women?

Answer 37

500 ml

Question 38

what's functional residual capacity?

Answer 38

the amount of air remaining in lungs at all time to stabilise the composition of alveolar air

Question 39

can functional residual capacity be measured by spirometry?

Answer 39

no

Question 40

what's Inspiratory Reserve Volume?

Answer 40

amount of air that can be forcibly inhaled after a normal tidal volume exhalation

Question 41

what's the average inspiratory reserve volume of males?

Answer 41

3300 mls

Question 42

what's the average inspiratory reserve volume of females?

Answer 42

1900 mls

Question 43

what's expiratory reserve volume (ERV)?

Answer 43

amount of air that can be forcibly exhaled after a normal tidal inhalation

Question 44

how is vital capacity measured?

Answer 44

VC= tidal volume (TV) + inspiratory reserve volume + expiratory reserve volume

Question 45

what is vital capacity?

Answer 45

the maximum amount of air that can be expired after maximum inspiratory effort

Question 46

what's the average vital capacity for males?

Answer 46

4800ml/ 4.8L

Question 47

what's the average vital capacity for females?

Answer 47

4200ml/4.2L

Question 48

what is inspiratory capacity?

Answer 48

maximum amount of air that can be inspired after a normal expiration

Question 49

how is inspiratory capacity calculated?

Answer 49

IC= Tidal Volume + inspiratory reserve volume

Question 50

how is functional residual capacity calculated?

Answer 50

FRC= residual volume + expiratory residual volume

Question 51

what is total lung capacity (TLC)?

Answer 51

max amount of air contained in the lungs after maximum inspiratory effort

Question 52

what's the average total lung capacity for males?

Answer 52

6L

Question 53

what's the average total lung capacity for females?

Answer 53

4.2L

Question 54

how is Total Lung Capacity (TLC) calculated?

Answer 54

TLC= Tidal volume + Inspiratory reserve volume + expiratory reserve volume + residual volume

Question 55

How does the respiratory system adapt to changing O2 demands? (2)

Answer 55

by varying: number of breaths per minute (rate) volume of air per breath (tidal volume)

Question 56

by what other name is pulmonary ventilation rate known?

Answer 56

respiratory minute volume

Question 57

what is pulmonary ventilation rate/ respiratory minute rate?

Answer 57

amount of air moved per minute

Question 58

how is pulmonary ventilation rate/ respiratory minute rate calculated?

Answer 58

tidal volume x breathing frequency

Question 59

what's the normal breathing frequency?

Answer 59

12-15 per minute

Question 60

for every 500ml tidal volume, how much doesn't reach the alveolar exchange surfaces?

Answer 60

150ml

Question 61

what's the purpose of the 150ml that doesn't reach the alveolar exchange surfaces?

Answer 61

to retain the integrity of conducting airways

Question 62

what's anatomical deadspace?

Answer 62

volume of air in conducting passages that doesn't participate in exchange

Question 63

what's alveolar ventilation?

Answer 63

amount of air reaching alveoli each minute

Question 64

how is alveolar ventilation calculated?

Answer 64

respiratory rate x (Tidal Volume- Anatomical dead space